1. Technical Field of the Invention
The present invention relates to liquid crystal devices for displaying various images, e.g., letters, figures, and drawings, by controlling alignment of liquid crystal enclosed between a pair of substrates, and particularly, to a liquid crystal device provided with an input unit such as a touch panel.
2. Description of the Related Art
With the spread of compact electronic information devices, such as personal digital assistants and palmtop computers, liquid crystal devices capable of input operations provided with transparent input sections overlaid thereon have been widely used.
As shown in FIG. 12, a known liquid crystal device capable of input operations is formed by bonding an input unit 94 including a flexible front substrate 94a and a back substrate 94b bonded to the front substrate 94a with a sealant 99, to a liquid crystal panel 92, including a first substrate 92a and a second substrate 92b bonded to the first substrate 92a with a sealant 93.
In this liquid crystal device, an image formed in the liquid crystal panel 92 is visible through the transparent input unit 94. When the outer face of the input unit 94, that is, the outer face of the front substrate 94a, is pressed with an input tool (a pen or a rod with a sharp tip), information on the location of the pressed portion is input.
However, in the conventional liquid crystal device capable of input operations, the input portion is locally deformed when the surface of the input unit 94 is pressed with the tip of the input tool. The deformation generates slight deflection in the first substrate 92a of the liquid crystal panel 92 which is stacked on the input unit 94. Since the gap between the substrates of the liquid crystal panel 92, that is, the cell gap, is at most 5 to 10 xcexcm, slight deflection of the first substrate 92a causes a significant localized change in the cell gap of the liquid crystal panel 92, resulting in a distortion pattern in the image displayed in the liquid crystal device.
Since the back substrate 94b of the input unit 94 is composed of a hard material such as glass, the device becomes heavy as the input unit 94 becomes thick. Thus, decreased thickness and weight of the device are barely achieved. The liquid crystal device having such problems inhibits trends toward decreasing the size and weight of portable electronic equipments.
Accordingly, the present invention solves the above problems. An object of the present invention is to reduce distortion of displayed images due to pressing operations of the input unit. Another object of the present invention is to achieve the configuration of a thin and lightweight liquid crystal device capable of input operations.
The present invention is characterized by a liquid crystal device comprising: a liquid crystal panel comprising a first substrate, a second substrate opposing the first substrate and having flexibility, and a liquid crystal layer disposed therebetween; and an input unit arranged at a position which lies at a position overlapping the liquid crystal panel in plan view at the first substrate side; wherein a gap is provided on a side of the second substrate away from the liquid crystal layer.
Also, the present invention is characterized by a liquid crystal device comprising: a liquid crystal panel comprising a first substrate, a second substrate opposing the first substrate and having flexibility, and a sealant and a liquid crystal layer disposed therebetween; an input unit arranged at a position which lies at a position overlapping the liquid crystal panel in plan view at the first substrate side; and a supporting section arranged at a position away from the liquid crystal layer of the second substrate; wherein the supporting section is arranged at a position corresponding to a region for forming the sealant.
The second substrate having flexibility is provided so as to be readily deflected along with the deflection of the first substrate. That is, the gap is provided on a side of the second substrate away from an image observing side, or the supporting section is arranged at a position corresponding to a region for forming the sealant.
When the a pressing operation is performed on the input unit, the first substrate is locally deflected by the pressing operation. The second substrate having flexibility is readily deflected along with the deflection of the first substrate. As a result, a localized change in the cell gap of the liquid crystal panel is suppressed.
When a position detecting element is disposed between the front-side substrate and the back-side substrate in the input unit and when the back-side substrate is directly or indirectly stacked on the first substrate, the input unit has a structure in which the position detecting element is disposed between these two substrates. Thus, this device can be produced by independently producing the input unit and the liquid crystal panel and by stacking them. Thus, the productivity and the yield of the device can be improved. Since the two substrates arranged on both sides of the position detecting element are flexible, the thickness and the weight of the input unit can be reduced.
Preferably, the second substrate has higher flexibility than that of a structure disposed between the position detecting element of the input unit and the liquid crystal of the liquid crystal panel. When the structure includes a plurality of components and when one component has significantly lower flexibility compared to the other components (for example, significantly thicker or significantly harder than those of the others), the flexibility of this structure may be substantially the same as the flexibility of the component having the least flexibility. This component may be the first substrate, or the back-side substrate when the back-side substrate opposing the front-side substrate with the position detecting means therebetween is provided in the input unit, or the illumination means (for example, a light guide plate) when the illuminating means for illuminating the liquid crystal panel is provided between the input unit and the liquid crystal panel. The pressure applied to the input unit by the pressing operation is absorbed by the above structure or the above member having hardness or low flexibility. The localized deflection of the above structure or the above member caused by the stress of the pressing operation to the input unit is suppressed by some extent due to the low flexibility thereof, but the deflection acts toward a localized change in the cell gap of the liquid crystal panel. Since the second substrate has higher flexibility than that of the structure or the member, the second substrate is also deflected in response to the deflection of the structure or the member so as to suppress a localized change in the cell gap.
Herein, xe2x80x9cflexibilityxe2x80x9d means a mechanical property causing relatively large deflection when a pressure (for example 0.5 to 5 N), which is generated when an operator puts an input tool into contact with a component, is applied. xe2x80x9cRelatively large deflectionxe2x80x9d in this case means a deflection which is the same or more than that of the cell gap of the liquid crystal panel (for example, 5 to 10 xcexcm or more). The flexible second substrate is effective for suppressing the display distortion of the liquid crystal panel caused by the pressing operations to the input unit. In contrast, the first substrate and the above member are preferably xe2x80x9chardxe2x80x9d or xe2x80x9cless flexiblexe2x80x9d. Herein xe2x80x9chardxe2x80x9d or xe2x80x9cless flexiblexe2x80x9d means a property causing a deflection (for example, 0.1 to 3 xcexcm or less) corresponding to a change in the cell gap which causes a change in the display state of the liquid crystal panel but not causing a deflection larger than the change in the cell gap when a pressure (for example 0.5 to 5 N), which is generated when an operator puts an input tool into contact with a component, is applied.
In addition, the supporting section is provided so as to directly or indirectly support the second substrate and the supporting section provides the gap at a side of the second substrate away from the operator. It is preferable that the supporting section support the second substrate in a peripheral region of the liquid crystal display region of the liquid crystal panel, because the supporting section securely supports the liquid crystal panel without affecting the cell gap and sufficiently absorbs the deflection of the second substrate. When the liquid crystal panel is provided with the sealant for enclosing the liquid crystal between the first substrate and the second substrate, the supporting section supports the second substrate at the position corresponding to the region for forming the sealant. Thus, the liquid crystal panel can be securely supported without deflection of the second substrate. Preferably, the supporting section extends along the region for forming the sealant and surrounds the gap in order to stably support the liquid crystal panel.
When an illumination means is provided for illuminating the liquid crystal panel with light from a side away the input unit, a gap is provided between the second substrate and the illumination means. The illumination means may have a light guide plate which deflects light from a light source towards the liquid crystal panel. In this case, the light guide plate faces the second substrate at the gap. The light guide plate may have a supporting section for directly or indirectly supporting the second substrate. A supporting section may be provided for directly or indirectly supporting the second substrate and the supporting section may provide a gap between the second substrate and the illumination means. The supporting section is preferably arranged at a position corresponding to a region for forming the sealant, as described above.
In this case, a so-called transflective panel may be formed by providing a reflective layer at the second substrate side and by providing an opening for transmitting the illuminating light from the illumination means to the reflective layer. This panel can be used as a reflective panel when the environment is bright or as a transmissive panel when the environment is dim.
Another possible idea is to provide an illumination means which illuminates the liquid crystal panel with light from a side of the observer. In this case, a reflective layer is provided at the second substrate side. Preferably, the illumination means is arranged between the input unit and the liquid crystal panel and has a light guide plate which deflects light from the light source towards the liquid crystal panel. Since the light guide plate provided between the input section and the liquid crystal panel absorbs the stress when the pressing operation is performed to the input unit, the distortion of the display in the liquid crystal panel during the pressing operation is suppressed. Preferably, the second substrate has higher flexibility than that of the composite structure of the light guide plate and the first substrate. Moreover, it is preferable that the first substrate also have flexibility in order to reduce the thickness and the weight of the liquid crystal panel.
When a casing is provided for supporting the input unit and the liquid crystal panel, it is preferable that the second substrate be directly or indirectly supported by the casing and the second substrate is provided with a gap at a side away from the liquid crystal layer. Preferably, the casing supports the second substrate at a position corresponding to a region for forming the sealant. The supporting section may directly or indirectly support the second substrate at a position corresponding to a periphery of the display region in the liquid crystal panel. When a sealant is provided for enclosing the liquid crystal between the first substrate and the second substrate, the casing preferably directly or indirectly supports at a position corresponding to a region for forming the sealant. In particular, the casing preferably has a supporting section which extends along the region for forming the sealant and surrounds the gap, in order to stably mount the liquid crystal device into the casing.
The liquid crystal device capable of input operations is built in various electronic equipments and functions as an input unit for inputting information to the electronic equipments. Examples of electronic equipments include information processing terminals, such as personal computers, including processing units such as a micro processor unit (MPU), electronic clocks and watches, such as wrist watches, communication devices, such as portable phones and facsimiles, and printing devices, such as printers and electronic copying machines.